1. Field of the Invention
The present invention relates to a vibration damping device adapted to provide vibration damping effect based on the striking action associated with bouncing displacement of an independent mass member housed within a hollow housing; and to a method for manufacturing such a device.
2. Description of the Related Art
One type of vibration damping device known to date is a vibration damping device of bouncing type having an independent, bouncing displacement-capable mass member accommodated within a housing that is fixedly attached to a component target for damping, and designed to afford vibration damping action through the impact energy and attenuation action produced when the independent mass component bounces inside the housing and repeatedly strikes against the housing upon input of vibration. Such as design is disclosed in U.S. Pat. No. 6,439,359, for example.
In such vibration damping devices of bouncing type, with a view to improving attenuating capability in order to more advantageously achieve vibration damping action, as well as achieving effective vibration damping action over a wide range of frequencies, it is effective to establish the distance between the outside peripheral face of the independent mass component and the inside peripheral face of the housing with a high degree of accuracy. That is, a high degree of dimensional accuracy is required at the inside peripheral face of the housing.
However, with the vibration damping device shown in the aforementioned U.S. Pat. No. 6,439,359, since the housing is fastened directly to the damped component through bolting, welding, or the like, it will be necessary for the housing to have sufficient strength in order to avoid diminished durability due to high stress in the fastened section. As a result, the housing is required to have both high strength and a high degree of dimensional accuracy as mentioned above, leading to an inherent problem that manufacture tends to be difficult owing to this fact. Specifically, where it is attempted, for example, to achieve dimensional accuracy without excessively high cost by using synthetic resin as the material for the housing, a difficulty of ensuring adequate strength as compared with a housing of metal or the like will be a problem that is typically encountered. Meanwhile, if the housing produced using metal or the like, the machining and structure necessary for achieving dimensional accuracy will be more complicated, with the risk of higher costs as compared with a housing of synthetic resin or similar material.
Moreover, the sections which fasten the vibration damping device to the damped component are disposed on the housing. Therefore, in the case when a vibration damping device is intended for installation on several different kinds of damped components, for example, some redesign of the housing will be necessary, even if the dimensions of the inside peripheral face of individual housings do not need to be redesigned, since the fastening structure to the different damped components will be different. A resultant problem is difficulty in achieving the advantages associated with improved production efficiency and lower cost.